It’s been a smoky week on the blog with news of the expansion at Kilchoman and a new release from Ardbeg. Therefore, we thought it would be a good idea to take a closer look at the ingredient that gives them their unmistakable flavour. So, here’s every question you’ve ever wanted to ask about peat, answered by whisky experts…
Ah, heavily-peated whisky. The great divider. The Marmite of the spirits world, if you will. For every die-hard Islay aficionado with a penchant for eye-wateringly medicinal, TCP-esque drams, there’s a bourbon connoisseur who wouldn’t clean their boots with the stuff. Such is life, and such is whisky.
Whatever your personal preference, you’re likely to have a few burning (ha) questions about the peat, specifically the mechanics involved in flavouring whisky with it. So, to quench your thirst for knowledge, we approached a selection of whisky experts to get the 4-1-1 on what is, essentially, thousands of years’ worth of decaying vegetation. Behold!
Where does peat come from?
Peat is formed in cold wetlands from partly decomposed vegetation – shrubs, heather, bog myrtle, forests – over thousands of years, explains Dr. Rachel Barrie, master distiller at BenRiach Distillery. It tends to be found close to the coast, “having formed when seas flooded the landscape, trapping the vegetation,” she explains. “Cellulose, lignin and other plant components decompose slowly over a seriously long time, due to the lack of oxygen being trapped underwater.” Grass, wood and moss break down in the peat, making it a very good fuel, as well as a source of smoky aromatics. Peat is found all over the world, “but is especially prevalent in the Northern hemisphere in places like Canada, Siberia and in particular Ireland and Scotland,” adds Cameron Ewen, bar manager and senior whisky ambassador in Edinburgh’s Balmoral Hotel.
Does peat exhibit terroir?
Peat exhibits the ‘terroir’ of the plant material trapped and compressed under swampy wetland, decomposing over thousands of years, says Dr Barrie. “As well as plant material, it’s influenced by the water that flooded the land,” she continues. As such, the peat found in the north east of Scotland differs to peat found on Islay, due to the higher proportion of forests and less wetlands. Not only do the Western Isles feel the full force of the Atlantic Ocean, says Ewen, but the peat on Islay also has a higher proportion of seaweed. By contrast, “northern peat tends to be more floral with decomposing heather and gorse playing important roles in this peat,” he explains. “This will usually give the whisky a drier smoky character more akin to a bonfire. The peat dug from mainland Scotland is composed mostly of leaves, grasses and woods. This usually lends a very soft smoke to the whisky often due to the amount of peat being used.”
How is peat harvested?
Traditionally, peat has been dug by hand, says Anthony Wills, founder and managing director of Islay’s Kilchoman Distillery, with machines introduced more recently as demand has increased. First, the top layer of turf would be peeled away, and then a trench anywhere from 0.5 metres to 2 metres deep would be dug, says Ewen. “Peat was then cut out of this trench and stacked in the fields to dry,” he says, usually for about six months until it became brittle. “This peat is then used in traditional kilns – oven-like structures capable of holding tonnes of damp barley – and the peat is burned to produce an aromatic smoke that dries the barley and gives the final whisky its distinct quality,” Ewen adds.
How and when are ‘phenols’ released?
The phenols are released when the peat fire is burning and the smoke impregnates the moist barley grains lying on a floor above the fire, Wills explains. The phenol level is measured in parts per millions of phenols (PPM). How long the fire is lit determines the level of PPM in the final malt. “In the old days peat was used to dry the malt down to 5% moisture, but the result was a very peaty, salty, phenolic whisky that wasn’t very refined,” says Wills. “Peating levels have now been refined by distillers, and peat is only used at the first stage and then switched to a warm air drying system.” As those who have tasted Bowmore and Laphroaig liquids side-by-side, each distillery usually has a preferred peating level they require for their malt. However, this measurement is not entirely accurate by the time the whisky is bottled, because the PPM reduces over the course of the whisky-making process, Ewan explains. “At every stage some of the phenols are lost – this is most noticeable in the distillation and maturation phase,’ he says. During maturation, “some of the phenols are absorbed or evaporate off”, while other notes mellow out over time.
Where does the peat burning tradition originate?
Historically the practice of using peat in whisky started through necessity, says Ewan. “Many distilleries were in remote parts of the country and as such, it was often impractical and not financially economic for distillers to use coal or oil in whisky production,” he explains. Peat had been used for centuries to heat bothies and blackhouses – traditional farmhouses – and this led to the practice being adopted by Scottish distillers. Those based further inland tended to use a mixture of coal, anthracite and peat, adds Dr Barrie, though the exact composition would have varied according to location, geography and terroir. That all changed in the 1970s, when natural gas was discovered in the North Sea and a boom of commercial barley maltings were built in the north and east. “With the readily available supply of natural gas, the larger commercial maltings rapidly became the most efficient, cleanest and scaled-up way to malt the barley,” she explains. “Without natural gas on Islay, peat continued to be the dominant source of fuel.”
In what other ways are distilleries using peat to flavour their spirits?
You don’t necessarily need peated barley to give your spirit a smoky taste. In fact, if you’re Daniel Szor, founder and CEO of England’s Cotswolds Distillery, you need only obtain an empty cask. “Our production director Nick and I went to visit our friends at Penderyn and were fascinated by one of their whiskies, which had been aged in a ex-Laphroaig quarter cask,” he explains. “As soon as we returned to the distillery, we ordered one from Speyside Cooperage and filled it with our unpeated new-make Cotswolds spirit.” After a year, says Szor, they were smitten. “ The cask provided just the right amount of phenols without overwhelming our delicate spirit, and the slight smokiness married perfectly with our rich and fruity Cotswolds spirit,” he says.